Tianjing TJ3000 Trial Cutting Report: Overcoming the Mass Production Bottleneck of 12-Inch Sapphire 1.25mm Thin Wafers

Abstract: In response to the technical pain points in the evolution of 12-inch sapphire substrates towards larger sizes and higher yields, the TJ3000 diamond wire multi-wire saw from Jiangsu Tianjing Intelligent Equipment has completed a specialized trial cutting verification. This trial used a 300mm diameter C-plane sapphire ingot with a target thickness of 1.25mm. The measured results are as follows: single-wafer warp ≤ 0.05mm, TTV ≤ 0.015mm, chipping depth < 10μm. Cutting efficiency improved by 40% compared to traditional equipment, with a stable yield exceeding 98.5%. This provides a deterministic domestic solution for the front-end processing of large-size Micro-LED substrates and RF devices.

1. Industry Pain Points: The "Size Curse" of 12-Inch Sapphire

In the field of semiconductor processing, sapphire (α-Al₂O₃), due to its excellent insulation, high thermal conductivity, and good lattice matching with GaN, is a core substrate material for LEDs, Micro-LEDs, and RF devices. As terminal displays demand higher pixel density and 5G RF requires enhanced thermal management, the substrate size transition from 6-inch, 8-inch to 12-inch (300mm) has become inevitable. However, the size increase poses geometric-level challenges to the slicing process:

Stress Concentration and Warp Loss of Control: A 12-inch wafer has 2.25 times the area of an 8-inch wafer. On a material with a Mohs hardness of 9, the "bow effect" caused by tension fluctuations in traditional saws is magnified. This easily leads to uneven stress release in the latter half of the cut, resulting in excessive warp (>0.1mm) and directly scrapping subsequent epitaxial growth.

Edge Chipping and Micro-Cracks: A thickness of 1.25mm lies between traditional thick wafers (>2mm) and ultra-thin wafers (<0.5mm), requiring the cutting wire to have sufficient rigid penetration force while avoiding edge "shell pattern" chipping caused by wire web vibration. If micro-crack depth exceeds 20μm, it will lead to a sharp increase in breakage rates during subsequent grinding processes.

Material Loss and Cost: A single 12-inch sapphire ingot is of extremely high value. Every 0.01mm increase in "kerf loss" during wire sawing means fewer finished wafers per ingot, directly raising BOM costs.

2. TJ3000 Technical Solution: Pendulum Swing and Full Servo Tension Closed-Loop

Addressing the above pain points, the TJ3000 adopts a pendulum cutting architecture with the workpiece descending from top to bottom and the diamond wire fixed. This design is not a simple mechanical inversion but a deep reconstruction based on fluid dynamics and material mechanics principles:

Tension Consistency (±0.1N): The equipment is equipped with a full servo motor tension control system. During the multi-hour 12-inch cutting cycle, wire web tension fluctuation is strictly controlled within ±0.1N. Compared to the tension drift caused by slurry viscosity in traditional slurry saws, the TJ3000 ensures uniform three-stage force distribution (entry, center, and exit zones) of the wire web through real-time feedback compensation, fundamentally suppressing warp.

Wire Speed and Cooling Synergy: The maximum diamond wire running speed is set at 2500 meters per minute, paired with a high-pressure internal cooling system to ensure grinding heat is instantly removed. For the 1.25mm thickness, we optimized the feed speed curve: low speed for crystal entry (to prevent edge chipping), high constant speed for the stable phase (to improve efficiency), and deceleration again at exit (to protect wafer integrity).

Pendulum Feeding: The unique pendulum mechanism causes the ingot to perform a micro-amplitude swing while descending on the Z-axis, changing the contact angle between the diamond wire and the material. This action effectively disperses single-point cutting stress, controlling the subsurface damage layer (SSD) depth to within 5μm. This lays the foundation for requiring only minimal subsequent grinding to meet polishing specifications, significantly saving grinding consumables and time costs.

3. Trial Cutting Data Interpretation: From "Capable of Cutting" to "Cutting Well"

This trial used an electroplated diamond wire (wire diameter 0.12mm) to perform continuous slicing of a 12-inch sapphire ingot, with a target thickness of 1.25mm per wafer.

Performance Metric                    Industry Standard (12-inch)          TJ3000 Measured Data              Technical Analysis

Total Thickness Variation (TTV)    ≤ 0.02mm                                          ≤ 0.015mm                                 High precision of full servo guideways ensures excellent wire web flatness

Warp                                             ≤ 0.08mm                                          ≤ 0.05mm                                Pendulum structure + constant tension effectively counteracts gravitational deformation

Surface Roughness (Ra)               ≤ 0.8μm                                              0.5~0.7μm                                 High wire speed produces fine cut marks, resulting in a shallow damage layer

Chipping Depth                           < 15μm                                              < 10μm                                       Precise matching of wire speed and feed enables a "soft landing"

Single Wafer Cutting Time           ~180 min                                           ~110 min                                 High wire speed and optimized process path significantly improve efficiency

Output Rate (Yield)                       > 95%                                                > 98.5%                                    Wire breakage rate < 0.1%, no material waste from mid-process stoppages

Key Finding: When cutting to the 15th wafer, the equipment sensors detected a slight increase in resistance due to wire wear. The system automatically triggered the tension compensation mechanism. The TTV data of subsequent wafers remained consistent with the first wafer, demonstrating the equipment's process stability during prolonged continuous operation.

4. Industrial Value: Paving the Way for 12-Inch GaN-on-Sapphire

1.25mm thick 12-inch sapphire wafers are currently primarily used for large-size Micro-LED mass transfer substrates and high-power RF filter substrates. The successful trial cut of the TJ3000 signifies that domestic equipment already possesses the capability to support the large-scale production of third-generation semiconductor materials:

Cost Reduction and Efficiency Improvement: A 40% increase in cutting efficiency, combined with a narrower kerf (0.12mm vs. traditional 0.18mm), allows a single 12-inch ingot to yield 2-3 more usable substrates, directly reducing the cost per substrate by approximately 15%.

Quality Leap: Extremely low warp significantly reduces the defect rate of "slip lines" during epitaxial growth. The reduced subsurface damage shortens grinding time from the traditional several hours to less than 1 hour, increasing production line throughput.

Import Substitution: The TJ3000, with a purchase cost less than one-third of imported equipment, achieves comparable or even superior processing precision. It breaks the long-term monopoly of Japanese and German brands in the 12-inch hard and brittle material cutting equipment market, providing a safe and controllable supply chain guarantee for the capacity expansion of domestic substrate manufacturers.

Conclusion:

The excellent performance of the Jiangsu Tianjing TJ3000 Diamond Wire Multi-Wire Saw on 1.25mm thick 12-inch sapphire wafers is not just a victory in equipment parameters, but a reflection of deep process understanding. We are committed to providing semiconductor processing professionals not just with a machine, but with a stable, efficient, low-loss slicing solution, supporting the steady and long-term progress of China's semiconductor materials industry in the 12-inch era.